A Note on Network Sampling in Drug Abuse Research

In this article we discuss a network sampling design that can be applied in drug abuse research at the community level. At this level often some partial sampling frame such as the register of a drug aid agency is available. This partial sampling frame can be used as the start of a network sample. Each selected registered drug abuser mentions his relationships with other drug abusers, and from those newly mentioned drug abusers who are not registered a second probability sample is drawn. Using this network sampling design the mean contact rates between clients, between clients and non registered drug abusers and between non registered drug abusers can be estimated despite the unknown total number of drug abusers. The design is illustrated by an analysis of the network data of the Heerlen Drug Monitoring System.